Method of and means for determining the heating value of combustible gases



April 19; 1927.

- 1,625,277 ll. N. PACKARD METHOD OF AND MEANS FOR DETERMINING THE HEATING VALUE OF COMBUSTIBLE GASES Original Filed Dec. 24, 1919 INVENTOR.

Momma 3L. 3

ATTORNEY 7 Patented Apr. 19,

UNITED s'rATEsv PATENT OFFICE.-

Homes 11. PACKARD, or wauwarosa. wrsconsm, ASSIGNOR TO THE comma-mm mm. (20., or MILWAUKEE, wrsconsm, A conrona'rron or wrsoousm.

mmon or AND arms roa DETERMINING THE HEAT NG 1 easns. I

VALUE OF comrrsmnn Application filed December 24, 1919, Serial No. 347,227. Renewed February 12, me.

This invention relates to amethodof and means for determining the heating value of combustible gases. v

While there has been a great demand for a practical calorimeter for this purpose and while various forms of such .calorimeters have been heretofore proposed .it is still the general practice to determine the heating value of combustible gases by laboratory tests and'calculations, the Calorimeters heretofore proposed being open to various objections, includin inaccuracy, unrcliablility of operation an inability to function con? tinuously. t

The present inventionhas among its objects to provide a method whereby the total heatin value of gases, asfdefinecl by the U. S. ureau of Standards, which value includes the latent heat of vaporization of the '2 water'of combustion, may be readily determin'ed with accuracy.

Anotherobject is to provide a reliable "calorimeter for carrying out such method, *such calorimeter to function continuously 2 and to record as well as determine the heating value of the test gas.

Another object is to provide a calorimeter of the aforesaid character wherein the heat given off by combustion of the test gas is transferred to a stream of fluid and the temperature rise of such fluid utilized in determining the heating value of the test g Various other objects and advantages of the invention will hereinafter appear.

The accompanying drawing diagrammatically illustrates one form of calorimeter for carrying out the aforesaid method and the same will nowbe' described, it being understood that the calorimeter illustrated may be modified in various ways without departin from the -sco e of-the appended claims.

ieferring to the drawing, a burner 1 is provided for the test gas, said burner'being enclosed within a tube 2 closed at itsnpper end whereby the products of combustion are forced to leave said tube throu h its lower end, The tube 2 is surrounded y a. tube 3 through which a stream of air is passed to absorb the heat given off by the burner through the tube 2. The stream of air passes upwardly through the tube 3 which is open at its upper end but provided with a cap 4 whereby the stream same is forced to. traverse a reflexed pat for a purpose hereinafter set forth.

of air after leavin the The products of combustion are thus prevented from mixing with the stream of cooling air and if the gas supplied to the burner is maintained at the temperature of the exit products of combustion. the water of combustion will be completely condensed from the products of combustion with the result A that the latent heat of vaporization of such water will be transferred to the stream of cooling air. Thus if the rate of flow of the cooling air and its temperature rise are accurately determined the total heating value of the test gas can be readily determined and if the rate of flow of the test gas and the cooling air are maintained roportional the temperature rise of the coo g air will be directly proportional to the heating value of t e as. e cooling air and test gas inclusive of a supply of air for purposes of combustion, are supplied in quantities bearing a constant ratio by three wet displacement meters 6, 7 and 8 which may be of standard form. However accurate quantitative proportionality of the test gas and combustion air is not necessary provided the air be supplied in moderate excess or at least in quantity sufficient to insure complete combustion under all conditions. The meter 6 supplies air to the tube 3 while the meters 7 and 8 respectively supply gas and air to a mixing chamber 9 associated with the burner and said meters are coupled together by any. suitable means represented by sprocket chains 10 and 11 for operation at given relative speeds.

- Further, all of said meters are mounted in a closed tank' 12 containing a quantity of water in which they are partially immersed is designed to force the incoming air into direct contact with the water to saturate the air and to bring its temperature to that of the water. The gasmeter is connected to a sup ly line 17 through a regulator 18 of standar form which functions to maintain a pressure on the inlet side of said meter equivalent to the air pressure within the tank, the gas being saturated in passing to the meter.

Thus provision is made for supplying air and gas to the meters under like temperature, pressure and saturation conditions and for maintaining a fixed speed ratio of the meters and hence assuming proper adjustment of the three streams of fluid the temperature rise of the stream of air to which the heat of combustion is transferred will always be directly proportional to the heating value of the gas regardless of its rate of flow. For example, assuming that for a given sample of gas the air to which the heat of combustion is transferred shows a temperature rise of 10.such temperature rise will obtain even though the rate of flow of the gas is doubled, for the rate of flow of the air will also be doubled. On the other hand, assuming the heating value of the sample of as to be reduced to one-half of that formerly assumed, the temperature rise of the air will be reduced to 5.

Resistance thermometers 20 and 21 of the armored type are provided in the tube 3 to measure the temperature rise of the air to which the heat of combustion is transferred, the thermometer 20 being arranged adjacent to the inlet end of said tube and the thermometer 21 adjacent to the outlet end such that with the arm of rheostat 29 in thereof. These resistance thermometers are utilized in a Wheatstone bridge for controlling the marker of a clock-driven B. t. u. recorder 22. The bridge is utilized to control a galvanometer 23 having associated with its needle 24 a switch 25 to control the operating magnets 26 and 27 of a ratcheting mechanism 28 which serves to both operate the marker of the recorder and a rheostat 29. The resistance thermometers are respectively connected to opposite terminals of the galvanometer and to one side of a D. C. supply circuit L-L', through the rheostat 29, while resistances 31 and 32 are respectively connected to opposite terminals of the galvanometer and to the opposite side of said D. C. circuit to complete the Wheatstone bridge. The arrangement is one position the resistance of said rheostat is divided equally between the circuits of the two resistance thermometers whereas movement of said arm from such position increases the resistance included in one thermometer circuit and correspondingly decreases the resistance included in the other thermometer circuit. Also the arrangement is such that for a given movement oi the rheostat arm the marker of the recorder is moved a given distance transversely of the chart of said recorder.

The switch 25 comprises two series of contacts 36 and 37 the contacts of one series to be successively engaged by the galvanometer needle when deflected in one direction and those of the other series to be successively enga ed thereby when deflected in the opposite irection. Further, the switch comprises two segments 38 and 39 carried by a reciprocable cross head 40 and operable to clamp the galvanometer needle be? tween the segment. 38 and any one of the contacts 36 or between segment 39 and any one of contacts 37. The contacts 36 and y 37 are supplied with current from a supply circuit L L which may be either A. C. or D. C. through a' contact drum 41 operated by the blower motor 15. The contact segments 38 and 39, on the other hand, are

respectively connected to the windings of I magnets 26 and 27 which have a common return to one side of the supply circuit L -L whereby operation of the switch 25 provides for energization of said switches selectively when the galvanometer needle is deflected from zero position. The segments 38 and 39 of the switch are operable by a solenoid 42 which is also controlled by the drum 41.

The drum 11 is provided with a segment 43 having one or more sets of spaced extensions 41, 45 and 46 of different lengths, said segments being provided to co-operate with contact brushes 17 to 51 inclusive. The segment 43-is designed to bridge brushes 47 and 18 to complete the circuit of solenoid 42 but only during a part of each revolution of the drum whereby continuous rotation of the drum will periodically energize and de-energize said solenoid for intermittent operation of the switch 25. All of the segment extensions are designed to co-operate with brush 49 to complete circuit to the outermost contacts 36 and 37 of switch 25 while extensions 45 and 46 are designed to co-operate with brush 50 to complete circuit to the intermediate contacts 36 and 37, extension -fl6 alone co-operating with brush 51 to complete circuit to the adjacent contacts 36 and 37. Thus assuming the segment to be provided with a single set of extensions and assuming the galvanometer needle to be deflected, a single revolution of the drum will provide for operation of switch 25 and for energization and de-energization of one of the magnets of the ratcheting mechanism either one, two or three times according to the degree of deflection of such needle. \Vhen the needle is only slightly deflected one revolution of the drum will cause only one step of operation of the ratcheting mechanism but when the needle is deflected to a greater degree one revolution of the drum will cause a proportionally greater number of operations of said mechanism.

heating Thus assuming the Wheatstone bridge to be balanced and the marker of the recorder properly positioned for the instant heating value of the test gas any variation in the value of the gas and consequent variation intemperature rise of the cooling air will unbalance the Wheatstone bridgeflcatues e cc 7 ing the alvanometer needle to be irection or the other; Thereupon the , rise of the cooling air varies in directpro-v portion to the change in heating value of the test gas. othe ratchetingmechanism' in so operating functions to operatethe rheostat in a step by step manner until the Wheatstone bridge is again balanced-thereby fl g alue-of the test gas. 1

temperature rise 0 plete transfer of heat from arresting the for makings continuous record of e heat- Moreover the ap aratus in i F the air compensates'for. the variables which must betaken intofeon sideration in determining of the test gas. Heat losses the burningas to the cooling airarc compensated by pass} i the stream of coolin airthrough the ei exed path above descri to preheat the incoming air after passing the inlet then; mometer. A certain amount of the heat transferred to the air is thus twice measured f -bust1ble fluid an definitely proportioned to andthe twice measured heat is so regulated that errors due to heat losses are eliminated.

On the other hand the resistances "of the I Wheatstone bridge are so designed as to;

45 compensate for variations of specific heater for variations ofthe heat-ingvalue of the I gas as measured due to its variable dilution the saturated air. with temperature and also with water vapor at different temperatures; Compensation for both variables may be ac complished'by designing the resistance thermometers for given changes in the resistance values thereof with given changes in the remperature and in the apparatus shown the resistance thermometers. are formed of 'suitable compositions of metals to-,afl?ord. them the desired characteristics. However, com-fpensation for such variables may be accomplished in other ways as by the provision of a variable resistance temperature difference coil in the Wheatstone bridge. Also, as will be understood, the Wheatstone bridge may bedesigned to compensate for; other variables not encountered in determining the heating value of the test gas by the method herein disclosed. h

" "'1. The

operation of the ratchetingmechanism. Thus the apparatus rovides" measuringthe "in the presence ofan I in a relation to transfer the heat of combustion to said second fluid." i'

the heating' value;

j: 3. The method of ascertainin due to in'eom ,heat of vaporization While in practice it 'i s preferred' to employ the above described Wheatstone bridge measuring and recording means because of I the accuracy and reliability thereof ;it is, ($1

ample, the thermometersQOgaIid 2-1} may be of known construction to function as recording thermometers or as'jelements. of a differential recording thermometer-.1

cure by Letters Patent'is: 1

method of ascertaining the heating value of a combustible" fluid which comprlses, efiecting ,com'bustionof such fluid in the presence of a suflicient quantity of air and determinin the efiectofcombustion upon a stream of air bearin' -a'definite quantity ratio to. the combustib -tained sep rate from the ;'cOmb1lSl;lQn prod ucts. i

2. The method "of ascertaining the heating value'of a combustible fluid 'What- I claimas new andjdesiife to se D which comprises determining the thermic effect uponfa stream of fluid whose temperature volume relation obeys the same physical lawas the test fluid ofacombustionj-" ofjthetest. fluidassured sufiiciency of combustion air and the heating value of a coiiibustible fluid which comprises efiecting complete combustion ofa quantity of such'fluid in air, and efiecting a heat transfer between the iresultant combustion products and a quantity' of a cooling fluid f og ,whose'temperature pressure volume relation obeys the same hysical law as said comthe quantity of said combustible fluid, and

effecting transfer to the cooling fluid of the I of any water produced by such combustion;

4. The method of ascertaining the heating value of acombustible fluid which comprises efiecting com lete combustion of a quantity ofjsuch flui n air, and efiecting a heat transfer between -theresultant combos tion products and a 'quantityof a cooling fluid whose temperature 'ressure volume relation obeys the same p ysical law as said combustible fluid and definitely proportioned J to the quantity of said combustible fluid, and efiecting cooli of the combustion products by 'the C00 in fluid to the temperature of the combusti 1e fluid prior to the heat transfer, to thereby prevent loss of heat of vaporization of any of such'prod ucts which are liquid at such temperature. v

5; The method of ascertaining the heating value of a combustible fluid which comprises, efiecting combustion of a complete combustion mixture of such fluid and air, and efiectinga heat exchange betweenthe resultant combustion products and a definitely proportioned quantity of cooling fluid, whose temperature pressure volume relation obeys the same physical law as said combustible fluid, under conditions, including counter flow of said fluids, such as to effect cooling. of the combustion products by f the cooling fluid to the temperature of the. combustible fluid prior to the heat transfer,

to therebyprevent loss of latent heat of vaporization of any of such products which are liquid at such temperature.

(3. The method of determining the heat ing value of a streannof combustible fluid by determining the total heating effect of the combustion thereof upon another stream of fluid, which comprises subjecting both fluids to like temperature, pressure and saturation conditions, supplying said fluids in streamsbearing a definite volumetric ratio to one another and maintaining the streams of said fluids separate during the heat transfer:

' 7. The method of ascertaining the heating value of a combustible gas by determining the effect of-the heat of combustion thereof upon a cooling fluid, which comprises subjecting the gas and cooling fluid to like saturation conditions, supplying the same in quantities having a definite ratio and eliminating the effect of variations in the heating value of the gas as measured due to its variable dilution with water vapor at different temperatures.

8. The method of ascertaining the l1eating value of a combustible gas by determining theeflect of the heat of combustion thereof on a cooling fluid, which comprises subjecting the as and cooling fluid to like saturation conditions, supplying the same in quantities having a definite ratio and eliminating the effect of variations of specific heat of the saturated air with temperature.

9. The method of determining the heating value of a combustible fluid which comprises subjecting to the heat of combustion thereof a cooling fluid supplied in a definlte quantitative proportion thereto, augmenting the apparent value of the temperature rise of the cooling fluid by causing a sup leniental transfer of heat thereto to there y compensate for heat losses incident to the first mentioned heat transfer, and measuringthe total resultant temperature rise of the cooling fluid. v

10. The method of determining the heating value of a combustible fluid which comprises subjecting a cooling fluid to the heat of combustion of the former fluid, such heat of combustion including the latent heat of vaporization of the water of combustion, proportioning the supplies of cooling fluid and combustion fluid for a definite quantity ratio thereof and measuring the temperature rise of the cooling fluid caused by-the heat of combustion.

11. The method of determining the heating value of a stream of combustible gas by measuring the temperature rise of a stream of cooling fluid subjected to the heat of combustion of such gas, which comprises supplying such gas and fluid under like temperature, pressure and saturationconditions, maintaining a definite volumetric ratio of the supplies of such fluids, augmenting the apparent resultant temperature rise of the fluid by causing a supplemental transfer of heat thereto to thereby compensate for heat. losses and eliminating the effect of variations of the heating value of the gas as supplied due to its variable dilution with water vapor at different temperatures.

12. The method of determining the heating value of combustible gases which comprises supplying under like temperature, pressure and saturation conditions test gas, air to be mixed therewith and a cooling fluid, maintaining definite volumetric proporti0nality of said gas and fluid, burning the mixture of gas and air and subjecting the cooling fluid to the resulting heat of combustion, and measuring the temperature rise of the cooling fluid resulting from the heat of c0mbustion.

'13. A calorimeter for determining the heating value of combustible gases by measuring the temperature rise of a'fluid subjected to the heat of combustion of the test gas and air, which includes means for subjecting the gas, air and fluid to like temper ature, pressure and saturation conditions and associated means for supplying said gas and fluid in continuous streams havin a definite volumetric ratio.

14. Apparatus for determining'the heating value of combustible gases including a plurality of wet dis lacementmeters to respectively supply tie test gas, combustion air and a cooling fluid, and means insuring substantial equalization of the temperatures of said meters.

15. Apparatus for determining the heating value of combustible gases including a plurality of wet displacement meters to respectively supply the test-gas and a cooling fluid and means insuring substantial equalization of the pressures of the gas and cooling fluid supp ied to said meters.

16. Apparatus for determining the heat-- lll jected to like temperature and pressure conditions. v 17. Apparatus for determining-the heatmg value of combustible gases including a plurality of wet displacement meters .to respectively supply the test gas and a cooling fluid, and a tankcontaining a quantity of fluid in which all of said meters are partially immersed to maintain like temperatures thereof,

18. Apparatus for determining the heating value of combustible gases lncluding a pluralit of wet disp'acement meters to respective y supply the test gas and air, a closed tank in which said meters are mounted, said tank being supplied with air under pressure for said air meter and a regulator within said tank to regulate the pressure of the gas supplied to said gas meter according to the air pressure within said tank.

19. Apparatus for determining the heating value of combustible gases including a -closed tank containing a flu'id, a plurality of wet displacement meters mounted there'- in to be maintained at like temperatures by such fluid, means for supplying said tank with air for certain ofi said meters and means forsupplying gas to another of said meters and regulating the pressure thereof to substantially equal the air pressure within said tank.

20. Apparatus for determining the heating value'of combustible gases comprising a burner, means for supplying under like temperature, pressure and saturation condi-' tions gas to be supplied to said burner and air to be supplied in proximity to said burner, said means supplying streams of gas and air whose volumes are in definite ratio and means for measurin the temperature' rise ofthe air subjected .to the heat given off by the burning gas inc'ludin means compensating for variations of the eating value of the gas as measured due to its variable dilution with water vapor at difierent temperatures.

21; Apparatus for determining theheating value of combustible gases comprising a burner, means for supplying under like temperature, pressure and saturation conditions gas to besupplied to said burner and air to e supplied 1n proximity to said burner,

' said means supplying streams of gas and air 'whosevolumes are indefinite ratio, means for measuring the temperature rise of the air subjected to the heat given ofi by the burning gas including means compensating for. variations of specific heat of the saturated air with temperature.

22. Apparatus for determining the heating value of combustible'gases comprising a burner, means for supplying under like temperature, pressure and saturation conditions gas to be supplied to said burner and air tobe suppliedin proximity to said burner, said means supplying streams of gas and air whose volumes I are in definite ratio, a means. for measurmg the temperature rise of the air subjected to the heat given of by the burning gas and means compensating for incomplete transfer of the h'eat of comv bustion to the air.

.23. Apparatus for determining the-heat-I ing value of combustible gases comprising a burner, means for supplying under like'temperature, pressure and saturation conditions 7 gas to be supplied to said burner and air to be supplied in proximity'to said burner, said means supplying streams of gas and air whose volumes are in definite ratio, means for measuring the temperaturerise of the an subjected to the heat of combustion including means compensating for variation of the heating value'ofthe gas as measured .80 due to its variable dilution with water. vapor at different temperatures, and means compensating for incomplete transfer of of combustion to the air. 7 I

24. In apparatus for determiningthe heating value of combustible gases, the com: bination with a burner of means to supply combustion gas thereto and also to supply a stream of'fluid in heat exchanging re t on to the products of combustion of the ga means for effecting counter flow of sai the heat fluid after such heat exchange to com en- I I sate for incomplete transfer of thecom ustion to the products ofv combustion of the gas, means for measuring the consequent temperature of said fluid, and means, for

transferring heat between the stream-of fluid after passing said measuring means and the apparatus for determining the...

same stream prior to passing said measuring means to thereby compensate for incomplete transfer of heat tosaid fluid during the earlier heat exchange.

26. pparatus for determining the heating va ue of combustible gases comprising a burner, means for supplying a stream of gas to the burner and astream of air in proximity to the burner and for maintainmg the stream of said air separate from the products ofthe g s combust on, said means supplying gas and air in quantities having a definite ratio and resistance thermometers in the path of said stream of air, whereby the temperature rise thereof due to the heat given oil by the burning gas may be measured.

27. Apparatus for determining the heat- I ing value of combustible gases compri bridge including resistance thermometers in the path of the stream of air to measure the temperature rise of the air caused by the heat given ofl by the burning gas and means controlled by said WVheatstone bridge for indicating the heating value of the test gas. 28. Apparatus for determining the heating value of combustible gases comprising a burner, means for supplying a stream of gas to the burner apd a stream of air in proximit to the burner, said means insurmg a de' nite quantity ratio of the gas and air supplied thereby, a Wheatstone bridge including resistance thermometers in the path of the stream of air to measure the temperature rise of the air caused by the heat given off by the burning gas and means controlled by said Wheatstone bridge for indicating and recording the heating value of the test gas.

.29. Apparatus for determining the heating value of combustible gases comprising a burner for the test gas, means for supplying a stream of cooling fluid in proximity to the burner and means for measuring the temperature rise of the cooling fluid caused by the heat of the burning gas, said measuring meansincluding electrical resistance influenced by changes in" temperature to com ensate for a variable factor tending to ren er the temperature rise of the cooling fluid disproportional to the heating value of the test gas.

30. Apparatus fordetermining the heat ing value of combustible gases comprising a burner for the test gas, means for supplying a stream of cooling fluid in proximity to said burner and means for measuring the temperature rise of the cooling fluid caused by the heat of the burning gas, said measuring means including a Wheatstone bridge havmg resistance therein influenced by chan es in temperature to compensate for a variable factor tending to render the temperature rise of the cooling fluid disproportional to the heating value of the test gas.

31. Apparatus for determining the heating value of combustible gases comprising a burner,'means for supplying a coolin fluid in proximity to said burner and a stone bridge having resistances to 'measure the temperature rise of the cooling fluid caused by the heat of the burning gas and to compensate for variable factors tending to render 'the temperature rise of the cooling -fluid disproportionate to the heating value of the test gas, such factors including variations of the heating'value of the 'gas due to its variable dilution with water vapor at different temperatures.

32, Apparatus for determining the heating value of combustible gases comprising a burner, means for supplying a stream of cooling fluid in proximity to said burner, a Wheatstone bridge including resistance thereatneat-ma all of said elements being co-ordinated to afl'ord continuous indication and recordation of theheating value of the test gas.

34. In a method of ascertaining the heat ing value of a flowing combustible fluid, through burning of such fluid and absorption by a proportionate flow of cooling fluid of the heat so liberated, the step which comprises effecting a heat exchange between the cooling fluidsubsequent to such absorption of heat thereby and the same fluid at a lower temperature.

35. In a method of ascertaining the heating value of a flowing combustible fluid, through burning of such fluid and absorption by a proportionate flow of cooling fluid of the heat so liberated, the step which comprises efl'ecting a heat exchange between the flow of cooling fluid after such heat absorption and the same fluid undergoing such heat absorption.

36. In a method of ascertaining the heating value of a flowing combustible fluid through quantitative proportioning of such fluid and a flow of cooling fluid, burning of such former fluid and absorption by the cooling fluid of the heat so liberated, the step which comprises effectin preheatin of the flow of cooling fluid by the same flui heated by such absorption. A

37. In a method of ascertaining the heating value of a combustible fluid through quantitative proportioning of such fluid and a cooling fluid,burning of such former fluid and absorption by the cooling fluid of the 'heat so liberated, the step which comprises utilizin the cooling fluid after subjection to such eat exchange for jacketing the fluid undergoin such heat exchange and for effecting a direct transfer of heat to the latter.

38. In a method of ascertaining the heating value of a combustible fluid through quantitative proportionin of such fluid and a cooling fluid, burning 0 such former fluid and absorption by the cooling fluid of the heat so liberated, the stepwhich comprises utilizing the coolin fluid after such heat exchange, for cjlacketmg and preheating the same fluid un ergoing such; exchange.

39. In apparatus or ascertaining the heating value of a combustible fluid, the

combination with means to efiect combustion of said fluid, of means for effecting a flow of fluid to absorb the heat of such combustion and means for causing a return flow of such fluid after such heat exchange for jacketing the fluid undergoing such exchange.

40. In apparatus for ascertaining the heating value of a flowing combustible fluid, the combination with means to effect combustion of said fluid, of means for effecting a proportionate flow of fluid to absorb the heat of such combustion and means for causing a return flow of such heated fluid for increasing the heat at a given point in the first mentioned flow.

41. In apparatus for ascertaining the heatingvalue of a flowing combustible fluid, the combination with means to effect combustion of said fluid, of means for causing the combustion products to flow in a given direction, means for effecting an opposite proportional flow of cooling fluid in heat exchanging relation to such combustion products. and means for causing said cooling fluid to flow in heat exchanging relation to its own flow during said first mentioned heat exchange to impart additional heat thereto.

42. In apparatus for ascertaining the heating value of a combustible fluid, the combination with means to effect combustion of said fluid. of means for causingthe combustion products to flow oppositely to and in heat exchanging relation to the flow of combustible fluid to said first mentioned means, means for causing a flow of cooling fluid in heat exchanging relation to said combustion products, and means for causand in heat exchanging relation to the combustible fluid prior to combustion thereof, means for causing an opposite flow of cooling fluid in heat exchanging relation to said combustion products. and means for causing a return flow of said cooling fluid to impart heat to its own flow during said last mentioned heat exchange, for substantially equalizing the temperatures of said cooling fluid and said combustion products.

44. In apparatus for ascertaining the heating value of a combustible fluid, the combination with means to effect combustion of said fluid, of means for'causing the combustion products to flow in heat exchanging relation to the flow of combustible fluid to said first mentioned means, means for causing a flow of cooling fluid adjacent to said combustion products to effect a further heat exchange, and means for causing a return flow of said cooling fluid for jacketing the fluids undergoing heat exchange and -for imparting heat to certain of the same.

In witness whereof, I have hereunto subscribed my name.

HORACE N. PACKARD. 

